InsulationMath: free insulationmath planning calculators
Quick answer: To figure out how much insulation you need, find your recommended R-value from ENERGY STAR (U.S.) or your provincial code with Natural Resources Canada guidance, measure the depth and type you already have, subtract, and convert the difference into inches and bags. Our free calculators do that math. If you see vermiculite, stop and do not disturb it.
Calculators
Hubs
How to use InsulationMath
- Find your target. See recommended R-value by zone or Canada R-value requirements.
- Measure what you have. Use a ruler in several spots; identify the material with the R-value chart.
- Calculate. The attic insulation calculator gives R and inches to add; the blown-in and batt calculators turn that into bags and packages.
- Seal and ventilate first. Read air sealing first and attic ventilation baffles.
- Budget. Use the cost calculator and savings calculator with your own prices.
- Decide who does it. See DIY vs hire and tools and PPE.
Our calculators
- Attic insulation: existing R, R to add, inches.
- Blown-in: bags from bag-chart coverage.
- Batt: packages from area.
- R-value stack: total R of layers.
- Shed: walls and ceiling of a small building.
- Spray foam: board feet and kits.
- Cost: your prices, your total.
- Savings: a rough yearly estimate.
All run in your browser. Nothing you type is sent anywhere.
Where our numbers come from
Recommended levels: ENERGY STAR and Natural Resources Canada. R per inch: typical published ranges, always overridden by the product label. Vermiculite guidance: Health Canada and the U.S. EPA. We do not publish prices or rebate amounts.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: an 800 sq ft attic in a U.S. Zone 4A home, empty of insulation, so ENERGY STAR's target is R60. With loose-fill at an assumed R2.5/in, you need 24 in settled. With an assumed bag coverage of 25 sq ft per bag at R60 and 10% waste: 800 ÷ 25 × 1.1 = 35.2, so 36 bags.
Why the order matters
Insulation is the last step, not the first. Hazards come first because you cannot safely work around vermiculite, damaged wiring or mould. Air sealing comes next because it is nearly impossible to reach leaks under 15 inches of fluffy insulation. Ventilation comes before insulating because baffles must go in before the eaves are covered. Then you insulate to the target and record the job. Following this order is what the official guidance from ENERGY STAR and NRCan points toward, and it protects both your comfort and your house.
Common situations
- Empty or nearly empty attic: aim for the uninsulated target in your zone; air seal everything first.
- Old, thin insulation: top up after sealing; see blown-in vs batt.
- Wet or contaminated insulation: fix the cause, remove damaged material, then insulate.
- Vermiculite: stop. Do not disturb it. Get professional advice.
- Shed or workshop: see the shed calculator.
- Basement or rim joists: see compare and the spray foam calculator.
What we will never do
We will not quote prices as facts, invent rebate amounts, promise savings, or tell you to disturb hazardous material. Every worked example on this site is labelled as illustrative, with assumptions you can change. When the official guidance and your local code disagree with a typical figure here, they win.
Canada and the U.S.
Most guides here apply in both countries. Where rules differ, we point to the right authority: ENERGY STAR and U.S. climate zones for the United States, and provincial codes plus Natural Resources Canada for Canada.
Glossary
- R-value: resistance to heat flow, imperial units.
- RSI: metric R-value.
- Loose-fill: insulation blown in by machine.
- Batt: pre-cut piece of insulation.
- Baffle: channel keeping soffit vents clear.
- Air sealing: closing gaps that let air move between house and attic.
- HDD: heating degree days, a measure of how cold a climate is.
How to use our calculators together
Start with the attic calculator to find the R you need to add. Use the blown-in or batt calculator to estimate material. Run the cost calculator with your local prices, then the savings calculator for a rough payback range. Each tool shows its assumptions, so you can change any number that does not match your home. For mixed layers, the R-value stack calculator adds them up, and the spray foam calculator handles board feet for rim joists and small areas. None of these tools replace a professional assessment, but together they help you plan a sensible, safe project.
A note on safety and sources
Our safety advice follows official sources. For asbestos and vermiculite we point to Health Canada and the U.S. EPA. For R-value targets we use ENERGY STAR's published table and NRCan homeowner guidance. Product labels, manufacturer instructions and your local code always take priority. If something on this site seems to conflict with them, follow the official source and let us know at the contact page.
Who this site is for
Homeowners and renters with permission, planning attic, wall, floor, shed or basement insulation in the U.S. or Canada, who want transparent maths and safety first. It is not a substitute for professional advice on hazards, structure, wiring or code.
Getting started today
Pick one step: check your attic for hazards from the hatch, measure the depth of existing insulation, and look up your climate zone. With those three facts you can use every calculator here.
Start with safety, then air sealing, then insulation, then records. That order rarely goes wrong.
FAQ
Is this site an energy audit?
No. It gives planning estimates; an energy advisor can assess your home.
Do you sell insulation?
No. We do not recommend brands or stores.
Can I use this in Canada?
Yes; use provincial code targets and NRCan guidance.